1. Field of the Invention
The present invention relates to a magnetic sensor unit, which is principle system of an actuator for an automobile and installed in the actuator.
2. Description of Related Art
A conventional magnetic sensor unit includes a magnetic circuit, for example, which converts electricity into driving force or torque. A position sensor is provided in the actuator that requires a precise driving mechanism, for example, the actuator for controlling intake valves of an engine of the automobile. The position sensor detects the rotating amount or the driving amount of members rotated or driven by the magnetic sensor unit. As a position detecting method of the position sensor, a magnetically detecting method, a contact resistance detecting method, an optically detecting method and so on are employed for the actuator. However, for example, the actuator for controlling the intake valves is placed in an engine compartment, which is a harsh environment for the actuator. Therefore, the magnetically detecting method is mostly often employed for the actuator for controlling the intake valves.
An oscillatory actuator having a magnetic position sensor is disclosed in JP-A-2000-88600. In this actuator, when a magnetic circuit inside an actuator motor is close to a magnetic flux detecting device, the magnetic flux detecting device detects leaking magnetic flux from the magnetic circuit. That is, there is a possibility that the magnetic flux detecting device cannot detect the magnetic flux of a sensor magnet accurately.